The present invention relates to valve action in relation to an internal conbustion engine in automobiles and, more particularly, to a desmodromic valve actuation system for intake and exhaust function of a four-stroke piston in such engines.
Valve action of internal combustion engines is required to control the piston chamber for four functions of intake, compression, combustion and exhaust. The proper timing for opening and closing these valves is extremely critical to effectively and efficiently produce the horsepower for an internal combustion engines. The standard method of controlling and operating these cams is initiated by a timing belt that connects the engine crankshaft to a camshaft. The camshaft has a series of cams, one for each intake and exhaust valve in each cylinder. The cams, as presently configured in all four cycle engines, are designed to displace the valve inwardly to open either the intake port or the exhaust port. The cams are incapable of closing the port openings; and, accordingly, springs, that are compressed when the cams open a port, are energized to provide forces that close the port. The energy merely supplies the force to return the valve to closed position when the energy is released, but the cam provides control of the valve. This control is necessary so that acceleration/deceleration of the valve can be accomplished with minimum impact loading of the valve seat and hence minimize noise. Further, the frequency of cycles for opening and closing of the valve is quite high requiring very high spring loading to accelerate the mass of the valve.
The four-cycle internal combustion engine requires a first cycle that is the intake wherein a mixture of gas and air enters an opened valve intake port. The piston is displaced vertically down the piston cylinder by the engine crankshaft. The second cycle is compression of the gas/air mixture. The piston is driven up the cylinder by the crankshaft. Both intake and exhaust valves are in a closed position to effectively seal the piston cavity and allow the pressurization of the gas/air mixture. At the appropriate time a spark is introduced to the mixture and an explosion occurs with rapid expansion of the resulting gases. The piston is driven down by the force of the expanding gas which in turn applies a resultant torque to the crankshaft. This torque when combined with a sequence of these explosions at additional pistons will result in the rotational energy of the engine and in its output horsepower. The final cycle is the return up the cylinder by the piston wherein the exhaust valve port is opened and allows gases to escape. At the conclusion of this cycle the next series of cycles is ready to commence by the intake cycle. It can be seen that the valve's closing and opening are essential in the process along with their control in the speed of their action and the duration they remain closed. It is desirable to operate these valves at the highest speed possible for effective and efficient power generation.
The opening of the valves by the camshaft is a positive mechanical operation by the individual cams. The closing of the valve is a kinematic action resulting from the energy stored in the spring to return and close the valve. This complete function severely limits the speed at which the engine can run, as the valve mass inertia is critical for the stored energy of the spring and limits the cycle time. The acceleration and deceleration of the cam for high cycling conditions can severely limit the size of the spring.
The normal function in the automobile engine is such that there is a firing sequence for the cyclinders that are constantly repeatable regardless of whether the car is parked or moving at any speed. Accordingly, the same displacement of gas/air mixture is constantly used regardless of speed or stopped. It can be seen that, when stopped, the engine uses much more gas than necessary, when all that is required is to keep the engine running can be accomplished with very minimal amounts of air/gasoline mixture. Power is required for accelerating a vehicle which requires richer mixtures and higher speeds of the engine. If the valves can be controlled during acceleration, efficient and effective volumes of mixture can be ingested in the cylinder for the appropriate condition of speed, thereby offering fuel economy. Finally, when achieving a desired speed it is only necessary to overcome the wind drag forces, the friction of the wheels on the road and the internal friction of the drive train and engine inertia to maintain the velocity. This can be accomplished with less than the total displacement put out by the engine. It would be desirable for effective gas consumption to have the ability to not only control the amount of air/gas mixture entering each piston but also have the ability to close any number of cylinders while the engine is performing with the remaining operational cylinders. Of necessity, the timing is critical for the closing down and reopening of the selected cylinders that become inoperative.
It is, therefore, the object of the present invention to provide means that will significantly reduce gas consumption of an internal combustion engine as typically found in an automobile by efficiently and effectively controlling valve port openness in concert with the requirements of the operation of a vehicle.
It is yet another object of the invention to present the means by which valve control is simple, precise and timely, which in turn will be in concert with the engine performance and results in immediate smooth sensitive control of the engine performance and in turn the automobile.
It is an additional object of the invention to provide the means for the necessary timing of the valve in a piston to be in sequence and in position relative to port opening and closing as well as acceleration and deceleration requirements of the valve.
It is also an object of the invention to present the means by which piston firing sequences and individual operations will be designed and controlled.
It is a further object of the present invention to provide a valve control system that is simplified in nature but more effective in controlling the percentage opening of valve ports and will completely eliminate the necessity of springs in the functioning of valves as found in present-day automotive internal combustion engines.
It is another object of the invention to provide a valve actuation system that will be considerably amenable to higher engine speed performance, enhancing the engine performance with resulting savings of gasoline.
It is a further object of the present invention to provide a simple robust construction of a valve actuator that is simple in operation and precisely controlled at all times.
It is a further object of the present invention to compensate for the thermal expansion and contraction of the valve stem during varying operating and ambient conditions to improve valve sealing.